chromium/chrome/test/data/extensions/api_test/service_worker/messaging/send_message_external/initiator/manifest.json

{
  "name": "Initiator extension for Messaging_ExternalMessageToWorker",
  "version": "0.1",
  "manifest_version": 2,
  "description": "Tests runtime.sendMessage and runtime.onMessageExternal between two SW based extensions",
  "background": {"service_worker": "service_worker_background.js"}
}